Chlorine Trifluoride Research Articles

Separation of a Gas Mixture Containing Uranium Hexafluoride, Hydrogen Fluoride, and Chlorine Trifluoride

Separation of a Gas Mixture Containing Uranium Hexafluoride, Hydrogen Fluoride, and Chlorine Trifluoride

Chlorine Trifluoride Gas Etching Design for Quickly and Uniformly Removing a Thick C-Face 4H-Silicon Carbide Layer

A process and a reactor for the quick, uniform and deep etching of a C-face 4H-silicon carbide layer were developed using chlorine trifluoride gas. Based on the concept that the etching rate profile of the rotating wafer was the average of that on a concentric circle, the uniform etching rate profile was obtained by the average between the multiple wavy etching rate profiles and by sufficiently spreading the chlorine trifluoride gas. The etching rate variation and RMS microroughness could be reduced to 1.6% and about 0.2 nm, when the etching rate and depth were 20 μm min−1 and about 100 μm, respectively. The developed process could etch off the 150-μm-deep layer without deteriorating the RMS microroughness for the total etching time within 8 min.

Chlorine trifluoride gas adsorption on the Fe, Ru, Rh, and Ir decorated gallium nitride nanotubes

The impact of decorating Fe, Ru, Rh, and Ir metals upon the sensing capability of a gallium nitride nanotube (GaNNT) in detecting chlorine trifluoride (CT) was scrutinized using the density functionals B3LYP and B97D. The interaction of the pristine GaNNT with CT was a physical adsorption with the sensing response (SR) of approximately 6.9. After decorating the above-mentioned metals on the GaNNT, adsorption energy of CT changed from −5.8 to −18.6, −18.9, −19.4, and −20.1 kcal/mol by decorating the Fe, Ru, Rh, and Ir metals into the GaNNT surface, respectively. Also, the corresponding SR dramatically increased to 39.6, 52.3, 63.8, and 106.6. This shows that the sensitivity of the metal-decorated GaNNT (metal@GaNNT) increased by increasing the atomic number of metals. As energy decomposition analysis revealed, the electrostatic, also known as cation-lone pair interaction, was mostly the nature of the interaction between the CT and metal@GaNNT.

Lowest Concentration of Chlorine Trifluoride Gas for Cleaning Silicon Carbide Chemical Vapor Deposition Reactor

A dilute chlorine trifluoride gas at less than 1% was possible for the cleaning of a silicon carbide chemical vapor deposition (CVD) reactor. For 20 min, the chlorine trifluoride gas at the concentrations of 0.5%–1% in ambient nitrogen at atmospheric pressure could detach the 30 μm-thick particle-type polycrystalline silicon carbide CVD film from the susceptor which had a coating film made of a purified pyrolytic carbon (PPyC). While the PPyC film had some damage due to the shallow fluorine diffusion, it could be recovered without any pit formation by annealing in ambient nitrogen containing a trace amount of oxygen at atmospheric pressure for 10 min at the temperature of 845 °C.

Sensing behavior of pure and Ni-doped BC3 to chlorine trifluoride: A computational survey

The adsorption of chlorine trifluoride (ClF3) was explored onto pure and Ni-doped graphene-like boron-carbide (BC3) nanosheets through density functional theory (DFT) computations. As ClF3 approaches the pure BC3 nanosheet, its adsorption releases 4.2–5.9 kcal/mol of energy, indicating a weak adsorption. Also, the electronic properties of the nanosheet do not change significantly. However, Ni-doping improves the performance of the BC3 nanosheet and makes it more reactive and sensitive to ClF3. Our standard Gibbs free energy of formation calculations indicated that replacing a B atom in the structure of the BC3 nanosheet with a Ni atom is more favorable than replacing a C atom. The electronic analysis indicated that the adsorption of ClF3 reduces the HOMO-LUMO energy gap of the Ni-doped BC3 nanosheet from 2.16 to 1.36 eV (∼−37.0%), which shows that the electrical conductivity of the nanosheet has increased. Thus, the Ni-doped BC3 nanosheet can generate electrical signals when the ClF3 molecules approach, which shows that this nanosheet is a promising sensor. The recovery time for the Ni-doped BC3 nanosheet was computed to be 5.4 s, representing a short recovery time.

Anticorrosive Behavior of Aluminum Nitride Surface Exposed to Chlorine Trifluoride Gas at High Temperatures

The powder and plate of aluminum nitride were exposed to chlorine trifluoride gas at the concentration of 100% and at atmospheric pressure for 10 min and temperatures up to about 1000 °C. With the increasing temperature, the weight of the aluminum nitride plate increased in the temperature range between 750 °C and 800 °C, while it decreased at temperatures higher than 800 °C. The thickness also increased at temperatures higher than 750 °C. The change in the aluminum nitride plate thickness showed a peak at 800 °C. The surface remained smooth at temperatures lower than 900 °C. However, the surface had small pits at 995 °C, because the aluminum trifluoride, produced by the chlorine trifluoride gas, was considered to slightly sublimate and affect the surface morphology. Overall, the aluminum nitride remained anticorrosive to the chlorine trifluoride gas at temperatures lower than 900 °C. When the aluminum nitride was used in the silicon carbide etching reactor, its surface was rather smooth after repetitive exposures to the chlorine trifluoride gas at 500 °C.

Photochemistry with Chlorine Trifluoride: Syntheses and Characterization of Difluorooxychloronium(V) Hexafluorido(non)metallates(V), [ClOF2 ][MF6 ] (M=V, Nb, Ta, Ru, Os, Ir, P, Sb).

A photochemical route to salts consisting of difluorooxychloronium(V) cations, [ClOF2]+, and hexafluorido(non)metallate(V) anions, [MF6]− (M=V, Nb, Ta, Ru, Os, Ir, P, Sb) is presented. As starting materials, either metals, oxygen and ClF3 or oxides and ClF3 are used. The prepared compounds were characterized by single‐crystal X‐ray diffraction and Raman spectroscopy. The crystal structures of [ClOF2][MF6] (M=V, Ru, Os, Ir, P, Sb) are layer structures that are isotypic with the previously reported compound [ClOF2][AsF6], whereas for M=Nb and Ta, similar crystal structures with a different stacking variant of the layers are observed. Additionally, partial or full O/F disorder within the [ClOF2]+ cations of the Nb and Ta compounds occurs. In all compounds reported here, a trigonal pyramidal [ClOF2]+ cation with three additional Cl⋅⋅⋅F contacts to neighboring [MF6]− anions is observed, resulting in a pseudo‐octahedral coordination sphere around the Cl atom. The Cl−F and Cl−O bond lengths of the [ClOF2]+ cations seem to correlate with the effective ionic radii of the M V ions. Quantum‐chemical, solid‐state calculations well reproduce the experimental Raman spectra and show, as do quantum‐chemical gas phase calculations, that the secondary Cl⋅⋅⋅F interactions are ionic in nature. However, both solid‐state and gas‐phase quantum‐chemical calculations fail to reproduce the increases in the Cl−O bond lengths with increasing effective ionic radius of M in [MF6]− and the Cl−O Raman shifts also do not generally follow this trend.

Recovery Method of Pyrolytic Carbon Surface after Exposure to Chlorine Trifluoride Gas

An annealing process was developed for the practical recover of a purified py-rolytic carbon (PPyC) surface from damage, such as color change and peeling, due to fluorination during exposure to chlorine trifluoride gas at high tempera-tures for the cleaning of a silicon carbide chemical vapor deposition reactor. The PPyC surface was annealed at 900°C for 10 min in ambient nitrogen con-taining oxygen at the concentrations of 0.01% - 20%. The rainbow-like colored surface returned to the dark gray color of the original PPyC. Simultaneously, the thin peeled films disappeared. The Raman spectra showed that the PPyC surface chemical bonding returned to that of the original one. The oxygen concentration as low as 0.01% could recover the PPyC surface along with re-ducing the surface pit formation, when the combination of the exposure to chlorine trifluoride gas and the recovery was repeated.

Hans Wolfgang Sachs (1912-2000) : From Nazi Volkstumskämpfer and chief pathologist of the Reich Physician SS to chairholder in the Federal Republic of Germany. English version.

During the Second World War, the German Wehrmacht and the SS tested various chemical warfare agents on prisoners of concentration camps. The SS needed a pathologist to do this. Therefore, Reichsarzt SS Ernst-Robert Grawitz recruited the 32-year-old Hans Wolfgang Sachs. Despite his position as senior pathologist at the office of the Reichsarzt SS, Sachs was spared interrogation and prosecution after 1945, although the prosecution presented a document about chemical warfare and human experiments during the Nuremberg medical trial. In this, Sachs was named as a participant in so-called “N-Stoff” (chlorine trifluoride) experiments. Little is known about Sachs to this day. This article is intended to close this gap. Of particular interest are the motives and reasons why Sachs joined the party and the SS, as well as his career after 1945.

Difluorochloronium(III) Fluoridometallates – from Molecular Building Blocks to (Helical) Chains

Difluorochloronium(III) compounds were synthesized from the reaction of metal powders (Ru, Os, Ir, Au), metal fluorides (NbF5, SbF3, BiF5) or a metal chloride (TaCl5) with excess liquid chlorine trifluoride. The compounds ClF2[AuF4], ClF2[MF6] (M = Nb, Ta, Ru, Os, Ir, Sb, Bi) and ClF2[Ta2F11] were obtained in crystalline form and their crystal structures were determined by single‐crystal X‐ray diffraction. The ClF2+ cations in the investigated compounds are bent, containing two strong, short, mainly covalent Cl–F bonds and two sterically active, free valence electron pairs in a pseudo‐tetrahedral arrangement. The coordination around the Cl atom is extended by two highly ionic, long fluorine bridges to neighboring fluoridometallate anions, resulting in a total coordination number of six. The crystal structures vary among the ClF2+ compounds and range from molecular building blocks, such as dimeric (ClF2[AuF4])2 and (ClF2[Ta2F11])2, to chains, some of which being helical, as in ClF2[MF6], (M = Nb, Ta, Ru, Os, Ir, Sb, Bi). Quantum‐chemical solid‐state and gas‐phase calculations were carried out to elucidate the bonding within the ClF2+ cations and their interactions with the bridging F atoms.

Design of a Silicon Carbide Chemical Vapor Deposition Reactor Cleaning Process Using Chlorine Trifluoride Gas Accounting for Exothermic Reaction Heat

A silicon carbide chemical vapor deposition reactor cleaning process was designed by managing and utilizing the temperature increase due to the exothermic reaction heat produced by the chemical reaction between chlorine trifluoride gas and a particle-type polycrystalline silicon carbide layer. The main issues were (i) the initial susceptor temperature, (ii) the exothermic reaction heat, and (iii) the heat transport from the susceptor surface for reducing the peeling of the susceptor coating film. The important parameter was the initial susceptor temperature for performing the moderate etching of the silicon carbide layer and the local etching at the contact point between the silicon carbide particles and the susceptor surface. The 30-μm-thick particle-type polycrystalline silicon carbide layer could be detached and cleaned in two minutes.

Etching Rate Profile of C-Face 4H-SiC Wafer Depending on Total Gas Flow Rate of Chlorine Trifluoride and Nitrogen

A 50-mm diameter silicon carbide wafer thinning technique by means of a chemical reaction using a chlorine trifluoride (ClF3) gas was studied accounting for the gas distributor design and the total gas flow rate. The entire etching depth profile could become uniform with the increasing total gas flow rate at the fixed chlorine trifluoride gas concentration. A relationship between the pinhole arrangement of the gas distributor and the local etching rate profile was clarified by comparing the quick calculation and the measurement.

Development of SiC Etching by Chlorine Fluoride Gas

Amorphous SiC and 4H-SiC were etched by chlorine fluoride (ClF), chlorine trifluoride (ClF3), fluorine (F2) and chlorine (Cl2) gases, in order to evaluate the etching capability of various reactive gases. The gaseous byproducts of SiC etching were observed by the quadrupole mass spectrometry. The ClF showed slow etching rate of amorphous SiC and 4H-SiC, while ClF3 and F2 quickly etched them. By the ClF gas, the etching rate of amorphous SiC was 120 nm/min at 400 °C. The ClF gas was expected to be suitable for a shallow etching, because of its moderate etching rate even at high temperatures.

Chemical Behavior of Byproduct Layer in Exhaust Tube Formed by Silicon Carbide Epitaxial Growth in a System Using Chlorides

This study evaluated the chemical behavior of an oily byproduct which was formed in the exhaust tube during the silicon carbide epitaxial growth process using various precursors, such as silanes, chlorosilanes, propane, hydrogen chloride and hydrogen. Most of the precursors were spontaneously emitted from the oily byproduct, when the oily byproduct was kept under a nitrogen gas flow at atmospheric pressure and at room temperature. When the oily byproduct was exposed to 2-5 % chlorine trifluoride gas in ambient nitrogen at room temperature, various gaseous fluorides were produced, accompanying a slight temperature increase.

SiC Epitaxial Reactor Cleaning by ClF<sub>3</sub> Gas with the Help of Reaction Heat

A silicon carbide epitaxial reactor cleaning process was designed accounting for the exothermic reaction heat between silicon carbide and chlorine trifluoride gas. To avoid the peeling of the susceptor surface coating film, the spontaneous temperature increase due to the exothermic reaction heat was moderated by adding the nitrogen gas. The particle-type silicon carbide deposition could be effectively removed without causing any damage of susceptor.

Non-Plasma Dry Etcher Design for 200 mm-Diameter Silicon Carbide Wafer

For improving the productivity of the semiconductor silicon carbide power devices, a very large diameter wafer process was studied, particularly for the non-plasma wafer etching using the chlorine trifluoride gas. Taking into account the motion of heavy gas, such as the chlorine trifluoride gas having the large molecular weight, the transport phenomena in the etching reactor were evaluated and designed using the computational fluid dynamics. The simple gas distributor design for a 200-mm-diameter wafer was evaluated in detail in order to uniformly spread the etchant gas over the wide wafer surface.

Synthesis and Characterization of the Hexafluoridomolybdates(V) A[MoF6] (A = Li – Cs)

The hexafluoridomolybdates(V), A[MoF6] (A = Li – Cs), were synthesized by reacting molybdenum pentafluoride (MoF5) with the alkali metal fluorides in anhydrous hydrogen fluoride (aHF) solution. Single crystals of A[MoF6] (A = Li, Na, Rb, Cs) were grown from solution and analyzed by single‐crystal X‐ray diffraction. The vibrational spectrum of each salt is reported in detail and compared to previously reported spectra. During analysis of the cubic modification of Na[MoF6] it was noticed that a phase transition occurs around 228 K. Some details regarding this phase transition are discussed. Attempts to determine the structure of the low‐temperature phase of Na[MoF6] lead to the observation of the Na[MoF6]·2HF solvate. Additionally, in an attempt to synthesize Na[MoF7] by the oxidation of Na[MoF6] in chlorine trifluoride (ClF3), a tetragonal modification of Na[MoF6] was observed. The crystal structures of the Na[MoF6]·2HF solvate and tetragonal modification of Na[MoF6] are also discussed in detail.

Preparation of Graphene Layers Using Microwave Exfoliation of Fluographite Intercalation Compounds

The work reports a study of the processes of multilayer graphene (MLG) preparation using the action of microwave (MW) radiation on polyfluoridedicarbon intercalation compounds with general composition C2F·xR (R is chlorine trifluoride, acetone, acetonitrile, carbon tetrachloride, and benzene). Under the action of MW heating, these intercalation compounds undergo exfoliation (splitting) at temperature values that are 40–55% lower than in the case of traditional convective heating. It is shown that microwave heating increases the exfoliation degree and specific surface area of fluorinated graphite and decreases residual content of fluorine and chlorine in MLG. A key role in the process of MW exfoliation is due to the absorption of MW radiation by the polar dielectric intercalated into the interlayer space of fluorinated graphite.

Synthesis and Characterization of the Tetrafluoridochlorates(III) A[ClF4] (A = K, Rb, Cs)

Single‐crystalline tetrafluoridochlorates(III) A[ClF4] (A = K, Rb, Cs) were synthesized from solvolysis reactions of alkali metal fluorides in liquid chlorine trifluoride. The structures were examined by means of single‐crystal X‐ray diffraction. K[ClF4] crystallizes in the K[BrF4] structure type, whereas the Rb and Cs compounds crystallize in the Li[AuF4] structure type. The compounds were further characterized by Raman and IR spectroscopy. Solid‐state quantum‐chemical calculations with hybrid density functional methods reproduced the experimental structures and enabled the interpretation of the experimental Raman and IR spectra.

Anticorrosive Behavior of SiCxNyOz Film Formed by Non-Heat Assistance Plasma-Enhanced Chemical Vapor Deposition Using Monomethylsilane, Nitrogen and Argon Gases

A SiCxNyOz film was formed on an aluminum substrate without any heating assistance using monomethylsilane, nitrogen and argon gases at 10–30 Pa by the parallel plate plasma-enhanced chemical vapor deposition method. The obtained film did not have any considerable pinhole and crack, based on the evaluation using a concentrated hydrogen chloride aqueous solution. The anti-corrosive behavior of the obtained film was studied by means of chlorine trifluoride gas etching at the concentration of 100% at atmospheric pressure and at various temperatures. The etching rate increased with the increasing temperature and with the increasing nitrogen concentration in the film. The increase in the nitrogen concentration in the film enhanced the fluorine diffusion through the film during the etching. The anticorrosive behavior was determined to be adjustable by the nitrogen concentration contained in the film.